A gas chromatograph-mass spectrometer (GC/MS) is provided with a gas chromatograph section and a mass spectrometry section. Sample components supplied to a column of the gas chromatograph section together with carrier gas are separated into each sample component in the process of passing through the column, and are sequentially lead to the mass spectrometry section and ionized, and mass spectrometry is thus performed (for example, see Patent Document 1).
FIG. 4 is a schematic cross-sectional diagram showing an example configuration of a conventional gas chromatograph-mass spectrometer. This gas chromatograph-mass spectrometer is provided with a gas chromatograph section (GC section 101) and a mass spectrometry section (MS section 102).
The GC section 101 is provided with a column 111, a sample vaporization chamber 112, a column oven 113, and an AFC (Auto Flow Controller) 114, for example. A sample component is supplied, together with carrier gas, to the column 111 from the sample vaporization chamber 112. The column 111 is provided inside the column oven 113, and during an analysis, a sample component may be supplied to the column 111 while the column 111 is being heated by a heater (not illustrated) inside the column oven 113.
As the carrier gas, He gas is used, for example. Carrier gas may be supplied to the sample vaporization chamber 112 through the AFC 114, and during an analysis, the flow rate of the carrier gas that is supplied to the sample vaporization chamber 112 may be adjusted by the AFC 114.
The MS section 102 is provided with a vacuum chamber (not illustrated), and the inside of the vacuum chamber may be placed in a vacuum state. During an analysis, a sample component separated by the column 111 may be lead to the vacuum chamber in the vacuum state to be ionized, and the ions may be detected by an ion detector (not illustrated), and mass spectrometry may thus be performed.
According to such a gas chromatograph-mass spectrometer, if the power of the device is turned off after an analysis is completed, it takes time for the vacuum chamber of the MS section 102 to fall into a vacuum state at the time of turning on of the power for the next analysis. Accordingly, even if there is time from completion of an analysis until the next analysis, the device is often kept in a standby with the power being on.
However, if the device is kept in a standby for a long time in a state where the power is on but there is no flow of carrier gas, the temperature of an ion source of the MS section 102 may be increased, possibly causing deterioration of the column 111 (especially the part immediately before the MS section 102). Accordingly, during a standby, column protection gas is sometimes caused to flow inside the column 111 to protect the column 111.
As the column protection gas, N2 gas is used, for example. In the example of FIG. 4, the column protection gas is supplied to the sample vaporization chamber 112 through the AFC 114, and is caused to flow from the sample vaporization chamber 112 into the column 111. On the upstream side of the AFC 114, an on-off valve 131 is provided on a channel 103 for the carrier gas (He gas), and an on-off valve 141 is provided on a channel 104 for the column protection gas (N2 gas).
Accordingly, during an analysis, the carrier gas may be supplied to the column 111 through the sample vaporization chamber 112 by placing the on-off valve 131 in an open state and the on-off valve 141 in a closed state. On the other hand, during a standby, the column protection gas may be supplied to the column 111 through the sample vaporization chamber 112 by placing the on-off valve 131 in a closed state and the on-off valve 141 in an open state.